我们有一个托管在 Azure 应用服务 (Windows) 上的 ASP .Net 8 Web API。它使用 Pomelo.EntityFrameworkCore.MySql 8.0.2 连接到 Azure Database for MySql 灵活服务器 v5.7。我们不使用专用访问/VNet。它是一个多租户应用程序，所有数据库都是InnoDB数据库。
当我们使用旧版 Azure Database for MySql SINGLE 服务器时，我们从未遇到过任何连接问题。它有 4 个 vCore 和 32 GB RAM。自从我们迁移到较新的 Azure Database for MySql FLEXIBLE 服务器（也具有 4 个 vCore 和 32 GB RAM）以来，我们偶尔（我的意思是每天可能有十几次）会遇到如下连接超时错误：
MySqlConnector.MySqlException (0x80004005): Connect Timeout expired.
---> MySqlConnector.MySqlException (0x80004005): Connect Timeout expired.
at MySqlConnector.Core.ServerSession.OpenTcpSocketAsync(ConnectionSettings cs, ILoadBalancer loadBalancer, Activity activity, IOBehavior ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/Core/ServerSession.cs:line 1046
at MySqlConnector.Core.ServerSession.ConnectAsync(ConnectionSettings cs, MySqlConnection connection, Int64 startingTimestamp, ILoadBalancer loadBalancer, Activity activity, IOBehavior ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/Core/ServerSession.cs:line 425
at MySqlConnector.MySqlConnection.CreateSessionAsync(ConnectionPool pool, Int64 startingTimestamp, Activity activity, Nullable`1 ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/MySqlConnection.cs:line 932
at MySqlConnector.MySqlConnection.CreateSessionAsync(ConnectionPool pool, Int64 startingTimestamp, Activity activity, Nullable`1 ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/MySqlConnection.cs:line 938
at MySqlConnector.MySqlConnection.CreateSessionAsync(ConnectionPool pool, Int64 startingTimestamp, Activity activity, Nullable`1 ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/MySqlConnection.cs:line 951
at MySqlConnector.MySqlConnection.OpenAsync(Nullable`1 ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/MySqlConnection.cs:line 419
at Microsoft.EntityFrameworkCore.ServerVersion.AutoDetect(String connectionString)
at PropWorx.API.Extensions.ConfigureExtensions.<>c__DisplayClass5_0.<DbContextConfiguration>b__0(DbContextOptionsBuilder options) in C:\Users\fabsr\source\repos\PropWorx.API\PropWorx.API\Extensions\ConfigureExtensions.cs:line 150
at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.CreateDbContextOptions[TContext](IServiceProvider applicationServiceProvider, Action`2 optionsAction)
at ResolveService(ILEmitResolverBuilderRuntimeContext, ServiceProviderEngineScope)
at ResolveService(ILEmitResolverBuilderRuntimeContext, ServiceProviderEngineScope)
at ResolveService(ILEmitResolverBuilderRuntimeContext, ServiceProviderEngineScope)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType)
at lambda_method134(Closure, Object, HttpContext, IServiceProvider)
at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddlewareImpl.Invoke(HttpContext context)
发生这种情况时，会持续大约一分钟，并会影响当时尝试连接的所有用户。此外，虽然我确实看到在该时间点执行的查询有所增加（可能是平时的两倍）——这很可能与连接超时有关——CPU 和 RAM 使用率都很低（大约 15%）并且连接计数远低于 4096 左右的限制（大约 500）。
我在 Web API 中使用的连接字符串非常基本：
$"Server={serverAddress};UserID={username};Password={password};Database={databaseName};SslMode=Required;TreatTinyAsBoolean=true;ConvertZeroDateTime=true;"
我正在使用EnableRetryOnFailure：
DbContextOptions<TenantContext> options = new DbContextOptionsBuilder<TenantContext>()
.UseMySql(connectionString,
new MySqlServerVersion(ServerVersion.AutoDetect(connectionString)),
builder => builder.EnableRetryOnFailure())
.Options;
这些是我们当前拥有的服务器参数：
aad_auth_only OFF
aad_auth_validate_oids_in_tenant ON
audit_log_enabled OFF
audit_log_events CONNECTION
audit_log_exclude_users azure_superuser
audit_log_include_users
audit_slow_log_enabled ON
auto_generate_certs OFF
auto_increment_increment 1
auto_increment_offset 1
autocommit ON
automatic_sp_privileges ON
avoid_temporal_upgrade OFF
azure_innodb_hpk_auto_add OFF
azure_innodb_hpk_show OFF
back_log 2831
basedir /mysql/
big_tables OFF
bind_address *
binlog_cache_size 131072
binlog_checksum CRC32
binlog_direct_non_transactional_updates OFF
binlog_error_action ABORT_SERVER
binlog_expire_logs_seconds 0
binlog_format ROW
binlog_group_commit_sync_delay 0
binlog_group_commit_sync_no_delay_count 0
binlog_gtid_simple_recovery ON
binlog_max_flush_queue_time 0
binlog_order_commits ON
binlog_row_image MINIMAL
binlog_rows_query_log_events OFF
binlog_stmt_cache_size 32768
binlog_transaction_dependency_history_size 32000
binlog_transaction_dependency_tracking WRITESET
block_encryption_mode aes-128-ecb
bulk_insert_buffer_size 8388608
character_set_client utf8mb4
character_set_connection utf8mb4
character_set_database utf8mb4
character_set_filesystem binary
character_set_results utf8mb4
character_set_server latin1
character_set_system utf8
character_sets_dir /mysql/share/charsets/
check_proxy_users OFF
collation_connection utf8mb4_general_ci
collation_database utf8mb4_general_ci
collation_server latin1_swedish_ci
completion_type NO_CHAIN
concurrent_insert AUTO
connect_timeout 10
core_file ON
datadir /app/work/data/
date_format %Y-%m-%d
datetime_format %Y-%m-%d %H:%i:%s
default_authentication_plugin mysql_native_password
default_password_lifetime 0
default_storage_engine InnoDB
default_tmp_storage_engine InnoDB
default_week_format 0
delay_key_write OFF
delayed_insert_limit 100
delayed_insert_timeout 300
delayed_queue_size 1000
disabled_storage_engines MyISAM,MRG_MyISAM,BLACKHOLE,FEDEATED,ARCHIVE
disconnect_on_expired_password ON
div_precision_increment 4
end_markers_in_json OFF
enforce_gtid_consistency ON
eq_range_index_dive_limit 200
error_count 0
error_log_enabled OFF
error_server_log_file OFF
event_scheduler OFF
expire_logs_days 0
explicit_defaults_for_timestamp ON
expr_analyzer_cache_type ON
external_user
flush OFF
flush_time 0
foreign_key_checks ON
ft_boolean_syntax + -><()~*:""&|
ft_max_word_len 84
ft_min_word_len 4
ft_query_expansion_limit 20
ft_stopword_file (built-in)
general_log OFF
general_log_file /app/work/serverlogs/mysql-general-propworx-san-mysql-flexible-server-57-uszr-2024021909.log
group_concat_max_len 1024
gtid_executed_compression_period 1000
gtid_mode ON
gtid_next AUTOMATIC
gtid_owned
gtid_purged 28ac0c76-cf0b-11ee-a869-6045bd41deab:1-425431,
8790a5c8-c67b-11ee-b686-6045bd41dbe2:1-1822618
have_compress YES
have_crypt YES
have_dynamic_loading YES
have_geometry YES
have_openssl YES
have_profiling YES
have_query_cache YES
have_rtree_keys YES
have_ssl YES
have_statement_timeout YES
have_symlink YES
host_cache_size 279
hostname ba3d1002be29
identity 0
ignore_builtin_innodb OFF
ignore_db_dirs
init_connect
init_file
init_file_string
init_slave
innodb_adaptive_flushing ON
innodb_adaptive_flushing_lwm 10
innodb_adaptive_hash_index OFF
innodb_adaptive_hash_index_parts 8
innodb_adaptive_max_sleep_delay 150000
innodb_api_bk_commit_interval 5
innodb_api_disable_rowlock OFF
innodb_api_enable_binlog OFF
innodb_api_enable_mdl OFF
innodb_api_trx_level 0
innodb_autoextend_increment 64
innodb_autoinc_lock_mode 1
innodb_buffer_pool_chunk_size 134217728
innodb_buffer_pool_dump_at_shutdown ON
innodb_buffer_pool_dump_now OFF
innodb_buffer_pool_dump_pct 100
innodb_buffer_pool_filename ib_buffer_pool
innodb_buffer_pool_instances 8
innodb_buffer_pool_load_abort OFF
innodb_buffer_pool_load_at_startup OFF
innodb_buffer_pool_load_now OFF
innodb_buffer_pool_size 25769803776
innodb_change_buffer_max_size 25
innodb_change_buffering all
innodb_checksum_algorithm crc32
innodb_checksums ON
innodb_cmp_per_index_enabled OFF
innodb_commit_concurrency 0
innodb_compression_failure_threshold_pct 5
innodb_compression_level 6
innodb_compression_pad_pct_max 50
innodb_concurrency_tickets 5000
innodb_data_file_path ibdata1:12M:autoextend
innodb_data_home_dir
innodb_deadlock_detect ON
innodb_default_row_format dynamic
innodb_disable_sort_file_cache OFF
innodb_doublewrite OFF
innodb_fast_shutdown 1
innodb_fatal_semaphore_wait_threshold 600
innodb_file_format Barracuda
innodb_file_format_check ON
innodb_file_format_max Barracuda
innodb_file_per_table ON
innodb_fill_factor 100
innodb_flush_log_at_timeout 1
innodb_flush_log_at_trx_commit 1
innodb_flush_method fsync
innodb_flush_neighbors 0
innodb_flush_sync ON
innodb_flushing_avg_loops 30
innodb_force_load_corrupted OFF
innodb_force_recovery 0
innodb_ft_aux_table
innodb_ft_cache_size 8000000
innodb_ft_enable_diag_print OFF
innodb_ft_enable_stopword ON
innodb_ft_max_token_size 84
innodb_ft_min_token_size 3
innodb_ft_num_word_optimize 2000
innodb_ft_result_cache_limit 2000000000
innodb_ft_server_stopword_table
innodb_ft_sort_pll_degree 2
innodb_ft_total_cache_size 640000000
innodb_ft_user_stopword_table
innodb_io_capacity 200
innodb_io_capacity_max 2000
innodb_large_prefix ON
innodb_lock_wait_timeout 50
innodb_locks_unsafe_for_binlog OFF
innodb_log_buffer_size 16777216
innodb_log_checksums ON
innodb_log_compressed_pages ON
innodb_log_file_size 268435456
innodb_log_files_in_group 2
innodb_log_group_home_dir ./
innodb_log_write_ahead_size 8192
innodb_lru_scan_depth 1024
innodb_max_dirty_pages_pct 75.000000
innodb_max_dirty_pages_pct_lwm 0.000000
innodb_max_purge_lag 0
innodb_max_purge_lag_delay 0
innodb_max_undo_log_size 1073741824
innodb_monitor_disable
innodb_monitor_enable
innodb_monitor_reset
innodb_monitor_reset_all
innodb_old_blocks_pct 37
innodb_old_blocks_time 1000
innodb_online_alter_log_max_size 134217728
innodb_open_files 10000
innodb_optimize_fulltext_only OFF
innodb_page_cleaners 4
innodb_page_size 16384
innodb_print_all_deadlocks OFF
innodb_purge_batch_size 300
innodb_purge_rseg_truncate_frequency 128
innodb_purge_threads 1
innodb_random_read_ahead OFF
innodb_read_ahead_threshold 56
innodb_read_io_threads 4
innodb_read_only OFF
innodb_replication_delay 0
innodb_rollback_on_timeout OFF
innodb_rollback_segments 128
innodb_sort_buffer_size 1048576
innodb_spin_wait_delay 6
innodb_stats_auto_recalc ON
innodb_stats_include_delete_marked OFF
innodb_stats_method nulls_equal
innodb_stats_on_metadata OFF
innodb_stats_persistent ON
innodb_stats_persistent_sample_pages 20
innodb_stats_sample_pages 8
innodb_stats_transient_sample_pages 8
innodb_status_output OFF
innodb_status_output_locks OFF
innodb_strict_mode ON
innodb_support_xa ON
innodb_sync_array_size 1
innodb_sync_spin_loops 30
innodb_table_locks ON
innodb_temp_data_file_path ibtmp1:12M:autoextend
innodb_thread_concurrency 0
innodb_thread_sleep_delay 10000
innodb_tmpdir /mnt/temp
innodb_undo_directory ./
innodb_undo_log_truncate OFF
innodb_undo_logs 128
innodb_undo_tablespaces 0
innodb_use_native_aio ON
innodb_version 5.7.44
innodb_write_io_threads 4
insert_id 0
interactive_timeout 28800
internal_tmp_disk_storage_engine InnoDB
join_buffer_size 262144
keep_files_on_create OFF
key_buffer_size 8388608
key_cache_age_threshold 300
key_cache_block_size 1024
key_cache_division_limit 100
keyring_operations ON
large_files_support ON
large_page_size 0
large_pages OFF
last_insert_id 0
lc_messages en_US
lc_messages_dir /mysql/share/
lc_time_names en_US
license GPL
local_infile ON
lock_wait_timeout 31536000
locked_in_memory OFF
log_bin ON
log_bin_basename /app/work/binlogs/mysql-bin
log_bin_index /app/work/data/mysql-bin.index
log_bin_trust_function_creators ON
log_bin_use_v1_row_events OFF
log_builtin_as_identified_by_password OFF
log_error stderr
log_error_verbosity 3
log_output NONE
log_queries_not_using_indexes OFF
log_slave_updates ON
log_slow_admin_statements OFF
log_slow_slave_statements OFF
log_statements_unsafe_for_binlog ON
log_syslog ON
log_syslog_facility daemon
log_syslog_include_pid ON
log_syslog_tag
log_throttle_queries_not_using_indexes 0
log_timestamps UTC
log_warnings 2
logical_server_name propworx-san-mysql-flexible-server-57-uszr
long_query_time 10.000000
low_priority_updates OFF
lower_case_file_system ON
lower_case_table_names 1
master_info_repository TABLE
master_verify_checksum OFF
max_allowed_packet 536870912
max_binlog_cache_size 18446744073709547520
max_binlog_size 104857600
max_binlog_stmt_cache_size 18446744073709547520
max_connect_errors 100
max_connections 2731
max_delayed_threads 20
max_digest_length 1024
max_error_count 64
max_execution_time 0
max_heap_table_size 16777216
max_insert_delayed_threads 20
max_join_size 18446744073709551615
max_length_for_sort_data 1024
max_points_in_geometry 65536
max_prepared_stmt_count 16382
max_relay_log_size 104857600
max_seeks_for_key 4294967295
max_sort_length 1024
max_sp_recursion_depth 0
max_tmp_tables 32
max_user_connections 0
max_write_lock_count 18446744073709551615
metadata_locks_cache_size 1024
metadata_locks_hash_instances 8
min_examined_row_limit 0
multi_range_count 256
myisam_data_pointer_size 6
myisam_max_sort_file_size 9223372036853727232
myisam_mmap_size 18446744073709551615
myisam_recover_options OFF
myisam_sort_buffer_size 8388608
myisam_stats_method nulls_unequal
myisam_use_mmap OFF
mysql_native_password_proxy_users OFF
net_buffer_length 16384
net_read_timeout 120
net_retry_count 10
net_write_timeout 240
new OFF
ngram_token_size 2
offline_mode OFF
old OFF
old_alter_table OFF
old_passwords 0
open_files_limit 22741
optimizer_prune_level 1
optimizer_search_depth 62
optimizer_switch index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=on,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosesc...
optimizer_trace enabled=off,one_line=off
optimizer_trace_features greedy_search=on,range_optimizer=on,dynamic_range=on,repeated_subselect=on
optimizer_trace_limit 1
optimizer_trace_max_mem_size 16384
optimizer_trace_offset -1
parser_max_mem_size 18446744073709551615
performance_schema ON
performance_schema_accounts_size -1
performance_schema_digests_size 10000
performance_schema_events_stages_history_long_size 10000
performance_schema_events_stages_history_size 10
performance_schema_events_statements_history_long_size 10000
performance_schema_events_statements_history_size 10
performance_schema_events_transactions_history_long_size 10000
performance_schema_events_transactions_history_size 10
performance_schema_events_waits_history_long_size 10000
performance_schema_events_waits_history_size 10
performance_schema_hosts_size -1
performance_schema_max_cond_classes 80
performance_schema_max_cond_instances -1
performance_schema_max_digest_length 1024
performance_schema_max_file_classes 80
performance_schema_max_file_handles 32768
performance_schema_max_file_instances -1
performance_schema_max_index_stat -1
performance_schema_max_memory_classes 320
performance_schema_max_metadata_locks -1
performance_schema_max_mutex_classes 200
performance_schema_max_mutex_instances -1
performance_schema_max_prepared_statements_instances -1
performance_schema_max_program_instances -1
performance_schema_max_rwlock_classes 40
performance_schema_max_rwlock_instances -1
performance_schema_max_socket_classes 10
performance_schema_max_socket_instances -1
performance_schema_max_sql_text_length 1024
performance_schema_max_stage_classes 150
performance_schema_max_statement_classes 196
performance_schema_max_statement_stack 10
performance_schema_max_table_handles -1
performance_schema_max_table_instances -1
performance_schema_max_table_lock_stat -1
performance_schema_max_thread_classes 50
performance_schema_max_thread_instances -1
performance_schema_session_connect_attrs_size 512
performance_schema_setup_actors_size -1
performance_schema_setup_objects_size -1
performance_schema_show_processlist OFF
performance_schema_users_size -1
pid_file /app/work/data/ba3d1002be29.pid
plugin_dir /mysql/lib/plugin/
port 3306
preload_buffer_size 32768
profiling OFF
profiling_history_size 15
protocol_version 10
proxy_user
pseudo_slave_mode OFF
pseudo_thread_id 1503866
query_alloc_block_size 8192
query_cache_limit 1048576
query_cache_min_res_unit 4096
query_cache_size 0
query_cache_type OFF
query_cache_wlock_invalidate OFF
query_prealloc_size 8192
rand_seed1 0
rand_seed2 0
range_alloc_block_size 4096
range_optimizer_max_mem_size 8388608
rbr_exec_mode STRICT
read_buffer_size 131072
read_only OFF
read_rnd_buffer_size 262144
relay_log /mnt/relaylogs/relay_bin
relay_log_basename /mnt/relaylogs/relay_bin
relay_log_index /mnt/relaylogs/relay_bin.index
relay_log_info_file relay-log.info
relay_log_info_repository TABLE
relay_log_purge ON
relay_log_recovery ON
relay_log_space_limit 8589934592
replication_optimize_for_static_plugin_config OFF
replication_sender_observe_commit_only OFF
report_host
report_password
report_port 3306
report_user
require_secure_transport OFF
rpl_stop_slave_timeout 31536000
secure_auth ON
secure_file_priv
server_id 2070254791
server_id_bits 32
server_uuid 28ac0c76-cf0b-11ee-a869-6045bd41deab
session_track_gtids OFF
session_track_schema ON
session_track_state_change OFF
session_track_system_variables time_zone, autocommit, character_set_client, character_set_results, character_set_connection
session_track_transaction_info OFF
sha256_password_auto_generate_rsa_keys OFF
sha256_password_private_key_path private_key.pem
sha256_password_proxy_users OFF
sha256_password_public_key_path public_key.pem
show_compatibility_56 OFF
show_create_table_verbosity OFF
show_old_temporals OFF
skip_external_locking ON
skip_name_resolve ON
skip_networking OFF
skip_show_database OFF
slave_allow_batching OFF
slave_checkpoint_group 512
slave_checkpoint_period 300
slave_compressed_protocol OFF
slave_exec_mode STRICT
slave_load_tmpdir /mnt/temp
slave_max_allowed_packet 1073741824
slave_net_timeout 60
slave_parallel_type LOGICAL_CLOCK
slave_parallel_workers 32
slave_pending_jobs_size_max 268435456
slave_preserve_commit_order ON
slave_rows_search_algorithms TABLE_SCAN,INDEX_SCAN
slave_skip_errors OFF
slave_sql_verify_checksum ON
slave_transaction_retries 10
slave_type_conversions
slow_launch_time 2
slow_query_log OFF
slow_query_log_file /app/serverlogs/slowlogs/mysql-slow-propworx-san-mysql-flexible-server-57-uszr-2024032809.log
socket /tmp/mysql/mysql.sock
sort_buffer_size 524288
sql_auto_is_null OFF
sql_big_selects ON
sql_buffer_result OFF
sql_log_bin ON
sql_log_off OFF
sql_mode STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER
sql_notes ON
sql_quote_show_create ON
sql_require_primary_key OFF
sql_safe_updates OFF
sql_select_limit 18446744073709551615
sql_slave_skip_counter 0
sql_warnings OFF
ssl_ca /app/work/ca.pem
ssl_capath
ssl_cert /app/work/cert.pem
ssl_cipher ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA384:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA256:DHE-RSA-AES128-CCM:DHE-RSA-AES256-CCM:DHE-RSA-AES128-C...
ssl_crl
ssl_crlpath
ssl_key /app/work/key.pem
stored_program_cache 256
super_read_only OFF
sync_binlog 1
sync_frm ON
sync_master_info 0
sync_relay_log 0
sync_relay_log_info 1
system_time_zone UTC
table_definition_cache 10000
table_open_cache 10000
table_open_cache_instances 16
thread_cache_size 35
thread_handling one-thread-per-connection
thread_pool_new_conn_high_prio OFF
thread_stack 262144
time_format %H:%i:%s
time_zone +00:00
timestamp 1711635902.056424
tls_version TLSv1.2
tmp_table_size 16777216
tmpdir /mnt/temp
transaction_alloc_block_size 8192
transaction_allow_batching OFF
transaction_isolation REPEATABLE-READ
transaction_prealloc_size 4096
transaction_read_only OFF
transaction_write_set_extraction XXHASH64
tx_isolation REPEATABLE-READ
tx_read_only OFF
unique_checks ON
updatable_views_with_limit YES
version 5.7.44-log
version_comment MySQL Community Server (GPL)
version_compile_machine x86_64
version_compile_os Linux
wait_timeout 28800
warning_count 0
抱歉，我不知道如何在这篇文章中粘贴 HTML 表格。 我的问题是，罪魁祸首还有什么可能？我还应该看什么？
我们的 API 代码没有任何变化。唯一改变的是 MySql Server 的类型。
第一个行动方案如下。
从 MySQL 命令提示符，
SET GLOBAL connect_timeout=30;
尝试 30 秒而不是 10 秒来让客户端连接。
如果这解决了您的问题，请更新您的 my.ini [mysqld} 部分。
您可能需要添加该行，因为默认时间为 10 秒。